The present invention relates to a fuel injection system for an internal combustion engine.
A very effective method for reducing those components of the exhaust gas of an internal combustion engine which are detrimental to health, and especially for the reduction of NO.sub.x components, is the recycling of certain quantities of the exhaust gas. Adding a gas to the combustion process which does not take part in the combustion itself results in a reduction of the combustion temperature so that fewer nitrogen oxides NO.sub.x are produced. In addition, the expelled exhaust gas quantity is also reduced. However, because gas exchange processes take place, the efficiency of the internal combustion engine deteriorates. Furthermore, at low rpm and especially during idling operation, the smooth running of the engine is affected. On the other hand, it is possible, in the partial load domain, to recycle relatively large amounts of exhaust gas in order to keep the NO.sub.x emission low and still maintain smokeless combustion. However, a large quantity of exhaust gas must be recycled. Advantageously, during idling operation, the exhaust gas recycling is small. In addition, the combustion temperature is lower and hence also the nitrogen oxide emission. In the partial load domain, however, the nitrogen oxide emission is especially high and therefore especially dangerous because in city operation, for which the most stringent exhaust gas regulations are applicable, most driving is done in the partial load domain. The regulations with respect to cross-country driving are less stringent, and in this type of driving, under full load, maximum power is required and the accumulation of toxic exhaust gases is less.